Electrical testing system



Patented Aug. 4, i925.

Y BARRY efr-FICE.: j

NYQUIST, orY EIMHURST, NnwyonxynssIeN'oR yiro AMERieAN TELEPHONEAND'TELEGRAPH-CQMPANY, A CORPORATION 0F' NEW YORK."

' 'nLEcTnacAn TESTINGLSYSTEM.

application fued :my V1e, 192i. seriai No'. $5,308.

all 'wheat t ma/ z/ concern.' r Be it'kn'ownl that I, HARRY siding atElmhurst, in the county of Queens mination of the degree-ofunbalance byapand' State of NewYork, have `invented certain Vimprovements vinElectrical Testing Systems, of which the following is a specification.fi! f This invention relates to electrical testing' y upon the amount of-unbalance existing between the line circuit and its balancing netsystems and particularly to anv arrangement for determining thedegree ofvunbalance ybetween two networks, such-as a signaling circuit and-thenetwork designed 'to vbalance the said circuit. l

f In order to operate most efficiently certain types of signalingcircuits, as, for example telephonerepeater circuits andrduplextelegraphv circuitsyit. is necessary to maintain a high degreeofbalance'between the line circuit andthe network which is intended to Abalance the said'circ'uit.- Y To attain thisresult, itis necessary todeterminefthe degree of unbalance'between a line circuit and itsbalancing network.v An

arrangement for determining the unbalance between a line and its networkin af-telephonel repeater circuit is shown in -thepatent yof Clark andCrisson, No. 1,407,983,granted Feb. 28, 1922'. Thisprovides for thedeterplying sinusoidalwaves of different frequen cies, preferablythroughout the voice range,

and determining the unbalance at each frev quency. Such a method ofmeasuring'is'de- `sirable in telephony because we are there Vconcernedwith [the steady-state condition,

but, in telegraphy the transient phenomena are of greater concern'.`

A telegraph signaling impulse'is slopedwave comprising a pluralitylofdiier- Aent frequencies which are simultaneously im pressed 'upon theline4 circuit wheneverv the key ofthe transmitting device'is closed. vIt

will accordinglyl be seen-tliatin telegraphy the transientVphlinomena'arejof vprime inip'ortance, land consequently, a measurementmade by a's'inusoidal wave of' a definite fre-Y quency does notgivecorrect results. j

It is well known'to those familiar with the art'of duplex telegraphythat if unbalance exists betweenV a liney circuit and a network NYQisT,re-

a steep,

' whi'ciivig designed@ 'simulate eicaieauyrthe i said, circuit, theapplication of signaling impulses yto the line circuit by the'transmitter` connected with" the 'terminal' circuit at one' end yof thesaid line. circuit .will cause the receivingrelay connected with. the,samefterminal circuit to respond 'to the transmitted signals, thedegree of response dependingl ,ment .of-the network .so that thereceiving relay willbeaii'ectedito the minimum extent bythe transmissionof signals from'that endv of the circuit at whichtherelay is located.

Although this linvention will be described` in connection with a"metallic duplex tele? graph circuit, `it is to be understood that it isnot limited to ithis particular. type of cir-r cuit,`but is capable ofmeasuring unbalances Y existing between any two types 'of networks.VThis invention will be better understood from' the'followingdescription when read in connection with the attached drawing of whichFigurelshows one form of embodiment of `the* invention andfF ig. 2 showsthe currentcurves 2, 2", 2, 'and 2d, which serve to'make V'clear` theprinciple upon" which the invention'.,IIefsts.A

In Fig-i1 a line circuit extends between two stations X and Y.'Connected with the line IJ at the station X is a balancing network N1the` function of whichis to balance" the's'aidline with respect to thetransmission ofgsign'aling impulses by the 'transmitter T1. Connectedbetween the? line L 7and its' net-l work N, is a receiving relay R1,having a plurality of windings designated 1, 2, 3, 4, 5 and G. Windings1, 2, 3 and 4 are of the same magnitude and are connected serially inthe line. Vindings 5 and 6 are connected in series with what is commonlyknown as the vibratory circuit. All of these windings are arranged uponthe same core, the magneto motive force of which is adapted to controlthe action of armature 7 of the receiving rela f.

Bi'idged across the junction point of windings 1 and 2, and the junctionpoint of windings 3 and 4 is the transmitting circuit 8, by means ofwhich signaling impulses from the transmitter T1 are effectively appliedto the line L for transmission to the receiving circuit at the distantstation Y. This transmitting circuit comprises in addition to thetransmitter T1 a transmitter-branch filter F, which is adapted to modifythe impulses generated by the transmitter T1 so that they will have awave shape which is best adapted to produce an arrival wave of the mostdesirable form at station Y, and at the same time to preventinterference with the telephone signaling currents which vmight betransmitted simultaneously over the cir'- cuit L.

It will be clearlyseen that the current impressed by the transmittingcircuit 8 will flow in opposite directions in windings 1 and 2, and alsooppositely in windings 3 and 4, and if the network N1 exactly balancesthe line L, the current will likewise be of the same magnitude in therespective windings so that no resultant flux will be set up on the coreand consequently no effeet will be produced upon the armature 7. If,however, there exists an unbalance between the network N1 and its lineL, the.

magnitude of the currents in the network and' the line will bedifferent, thereby affectingthe armature 7. The object of this inventionis to determine the degree of unbalance that exists between the networkand its line and to eliminate or reduce the unbalance by properadjustment.

The vibratory circuit, in which the windings 5 and 6 are located, alsocontains a condenser 9 and a resistance 10, the Jfunction of which willlater be made clear inl the description of the operation of the circuit.Bridged symmetrically across the vibratory circuit, between the junctionpoint of windings 5 and 6, and the junction point between condenser 9and resistance 10 is a circuit containing the armature 7 and its.associated apparatus. The `armature 7 whichV is con'- nected byconductor 30 with the midpoint of windings 5-6, is adapted to movebetween contacts 11 and 12, with which are connected batteries 13 and 14of opposite polarity. Connected between the batteries 13 and 14 are theresistances15 and 16, the

junction point of which is connected by conductor 31 with the polarsounder 17 and tl'irough the resistance 18 to the vibratory circuit atthe junction point between condenser 9 and resistance 10.

The terminal circuit at station Y is similar to the circuit at stationX'as described above and needs no further explanation.

Bridged across the conductors 30 and 31 is the winding 19, which isadapted to control the movement of the arma-ture 20 connected to one ofthe corners of the distortion bridge, which is of the type shown anddescribed in the patent to Nyquist 1,435,323, dated Novemberl 14, 1922.Connected with the correspondingly opposite corner of the said bridge isanother armature 21, the

movements of which are controlled bythe flow of' current in the winding22 which is connected with a transmitting device 23, designed to beoperated in synchronism with the transmitter T2 at station Y except4that it operates with a lag which is made'substantially vequal to thelag produced by the telegraph system. This bridge is so designed thatwhen the armatures 20 and 21 are in the position lshown in the drawing,or when the armatures are upon corresponding contacts, that is to say,when armatures 20 and 21 are upon contacts of A and B respectively, orupon contacts of C and D respectively, the bridge remains balanced andno current will flow through the path containing the galvanometer G. If,however, one of the armatures is in its neutral position and the otherarmature has closed either one of its contacts, or if the said armaturesare upon oppositely disposed contacts the bridge will be unbalanced andthe magnitude of the unbalancing currentV will be indicated by thegalvanometer.

Having in mind the foregoing description of the apparatus shown in thedrawing, the invention will be clearly understood from the followingdescription of the mode of operation of the circuit in which it. isembodied. Y

This invention is based upon the principle of beating together twowaves, each comprising a series of reversals of two differentfrequencies and detecting the variations in the operation of thearmature of thereceiving relay resulting from the effect of unbalancebetween the line circuit and its balancing network. Let it be assumedthat rel OO versals ofva frequency f are being transmitted by theytransmitter T2 over the line L soV as to operate the armature 7 Y ofthe receiving relay and that nosignals are being transmitted by T1. Whenthe current from the transmitter T2v flows through the windings 1-2 and3 4 in a definite direction, it will move the armature 7 to one of itscontacts, as for example, 12. Current will then flow from batteryf14through contact the opposite side ofthe battery.v Thiswill chargekthelcondenser 9,LA located infthe vif Furthermore, thel flow offdirecti'onsv Vfrom their respective junctionpoints therewill be noresulting magnetiza`-- bratory circuit. current through the; winding`will be in such direction'as to create a magneto-motive force .whichwillhave v.such effect upon `the armature-.7 as to tendto-pull it away from:

the contact 12,-'although it will not affect the l.actual opening ofthis contact Solong as theline current from thetransmitter T21 tends toflow in lthe vpreviously assumed direction through the line Vwindings ofthe,

relay R1. fWhenftheline current through the windings 1-2 and. 3 4, fallsbelow a certain minimum value the condenser 9 willA discharge through avcircuit comprising'the windings 5 and' 6 Yin` series with Vtheresistance V10, andthe resultant discharge of our# rent through thesewindings'will be in such direction ask to move, the armature 7 quicklyfrom contact 12. Since it has been assumedv that .the wave beingtransmitted by the transmitter,T2 constitute aseries of reversalsotfrequency f, such as 'shown by` curve 2a, the reversal of the currenton the line L and in the windings 1-2 and -ftwill move thearmaturetocontact y11 andwill cause current of positive-.polarity to flowthroughr the vibratory circuit, charging the condenser Qin anoppositesense.- The fiow of currentthroughthe winding 6 will ybe in' aVdirec-V tion as will tend; to i lcause the armature y 7 to move awayfrom contact 11 Vand this will be affected by theaction ofthe dischargeotrcondenser -9 Athrough the windings 5 and 6, as 'soon as the currentinthe line windings falls kbe'low,a deiinite yminimum amount. Thepurposeof this vvibratory circuit is'to overcome the sluggish actionofthearmature T'fwhen thecurrentjin v.the line circuit reverses, as inthe sending of marking and spacingfsignals, and provides therefor ameans for obtaining quick positive action1 of the receiving relay.Therefore thel receipt of a series of reversals of frequency flvasrepresented by'curve' 27 will cause uniform operation of the receivingrelay.

Now, assumethat whilefthe transmitter Tf2 at station Y'is beingoperatedto send overthe line L vreversals of frequency f, the transmitter T1 issimultaneouslyoper-A ated for fthefpurpose, of transmitting fromstationXto sta-tion Y, a series of current ref versals of frequency f.which may be `either slightlyrgreater or less thantwice @the i're.-quency f of the signals sent over the lineL by the transmitter T2. The`current from the transmitter ',Tl, is impressed by the transmittingcircuit 8 across the lineL at the junction points between the windings1-2 and the windingsv 3-4. This current divides, `part of it flowingythroughthe winding llover the line L and back through the winding 4, andthe other part -tlowing through the winding 2 through the. line bal-`ancing ,network N1 andl thev vwinding 3.

Since theselwindings are uponthe Sameicore,

and sincerthe How of currentis yiii-opposite Y tion'fofthecore if thecurrents| are equal, which means if the line balancing networkexactlybalances the line L. If, however,`

there. exists anV unbalance between the line balancing network and theline circuit, the.y

the unbalance current that tends -to magnetize the core of the relay R1and there fore to operate the armature Y2' and has, for example, beenassumed` to be slightlyless than 2f. It is ythe difference in thecurrent that flows from the midpoint of thewind-V ings Ri throughtheline and and through the'line balancing network N1. This re-A wiseproduces irregularityof operation `of f the armature 7. .The armaturewill not remain upon itscontacts for equalperiods of,

time since the time that it will'remain upon any one conta-ctvwilldepend upon`thedura tion of the magnetizing current.

The impulses resulting from the action of the armature will beimpressedupon the winding 19 which controls thearmature 20 connectedwith one of the corners of the distortion bridge. application of currentto the winding 19 there will be impressed upon the Winding 22a currentwave of thesame magnitude and phase as shown in curve 21, which is thecurve of the current set up by the transmitter T2 as corrected for thelag due toy transmission over the line. -The currents inthe windings l19and 22 will causetheir corresponding armatures to 'touch theirright-hand or yleft-hand contact points, depending upon the direction offlow of current `through the windings. If the currents in the twowindings were identical in phase and magnitude, the positions oftheAarmatures20` and 21 would at all times Vcorrespond, that is to say,that at any instant ofk time both armatures would be on their right-handcontacts or their left-hand contacts, or in the neutral position betweenthe contacts. Since, however, thecurrent arriving over the line L fromthe transmitter T2 has superimposed thereon the unbalance current of thetransmitter T1, which exists by virtue of the imbalance between the lineand its balancing network, the current flowing inthe winding 19 will notbe in the same phase as the current flowing-through the winding 22 andconsequently the movement of the armature 2() will not be insynchronisin with the movement of the armature 21. rlhe movement of thearmature 2O into contact with either of its contact points in advance ofthe time when the armature 21 comes into contact with the correspondingcontact point will produce on imbalance in the bridge network, whichimbalance will be indicated by the movement of the needle of thegalvanoineter G. Adjustments are then made on the artificial line whileobserving the periodic change in the reading given by thev distortionbridge galvanometer needle. This adjustment is continued until theneedle indicates the minimum variation throughout a definite period oftime which indicates the minimum imbalance between the lines and itsbalancing network.

VIt will be seen that the method of detei'- mining the degree ofimbalance between two networks comprises the simultaneous impression oftwo periodic signaling waves upon a relay, the frequency of one of thesignaling waves being slightly greater or less than double the frequencyof the other signaling wave, and allowing the resultant magnetizingcurrent to control the operation of the armature of the relay, thefreqiiencyV of operation of which closely follows the frequency of thecombined waves.

Byvimpressing the impulses resulting from the action of the armatureupon one of the windings of the distortion bridge, as shown in myapplication, Serial No. 353,- L16 filed January 23, 1920, and simultane-Y oiisly impressing upon another winding of the distortion bridge a wavehaving the same frequency and shape as the lower frequency signalingwave, the extent of the imbalance between the line network and the linecircuit may be determined, and the line network may be adjusted untilthe point of minimum imbalance is obtained.

'Although this invention has been disclosed as having a. definite formand arrangement of parts it is to be understood that it is capable ofembodiment in other and different forms without departing from thespirit and scope of the appended claims.

What is claimed is:

1. InV an electrical testing system, the method for determining thedegree of unbalancev between two networks, which consists insimultaneously transmitting and receiving telegraph signals of differentfrequencies, and 'indicating the distortion ofV the received signals bylthe transmitted signals. i

2. In an electrical testing system, the method forv determining thedegree of unbalance between a line circuit and its balancing circuit,which consists inA simultaneously receiving and transmittingtelegraphsignals, the respective signals. being of different frequencies,allowing the said signals to actuate a signal receiving device, andindicating the distortion of the received signals by the transmittedsignals'due to unbalance between the line circuit and its balancingcircuit.

V3. In an electrical testing system, the method for determining thedegree of unbalance between two electrical networks, which consists inimpressing signaling impulses of different frequencies from separatesources upon the said networks, allowing the impulses from one of saidsources to interfere with the impulses from the other of the saidsources in proportion to the degree of unbalance between the twonetworks, and determining the degree of imbalance byvirtue of the degreeof distortion produced in the impulses from the other of said sources.

4L. In an electrical testing system, the method for determining thedegree of unbalance between two electrical networks, which consists increating signaling imp-ulses of different frequencies, impressing saidimpulses of different frequencies simultaneously upon the said networks,beating together the said frequencies, and determining the degree ofunbalance betweenthe said networks by virtue of the beat frequencyproduced.

5. In an electrical testing system, the method for determining thedegree of unbalance between two electrical networks, which consists increating signaling impulses of different frequencies impressing saidimpulses simultaneously upon the said networks, beating together thesaid frequencies, and allowing the resultant frequency to control anindicating device whereby the degree of distortion resulting fromunbalance between the said networks may be determined.

6. In a duplex telegraph signaling system characterized by a pluralityof transmit-- ting circuits, a line circuit connecting said transmittingcircuits, a balancing circuit, a receiving circuit having distortionindicating means associated therewith, and means for electricallyrelating the said balancing circuit and receiving circuit with the saidline circuit and one of said transmitting circuits, the method fordetermining the degree of unbalance between the line circuit and itsballlt) anoing circuit', which; consists''ioff'inlipre'ssinglsimultaneously acrossv the saidl linefcircuity "at opposite ends thereoftelegraph signalsfof different fre'opiiencies,`v beating .together;v thesignals of the' saidffrequencies 'and comparingntliev resultantfrequency with? that im'-l pressed uponfthe said line circuit at thedist-ant end thereof whereby the degree of unbalance between the linecircuit and lthe balancing circuit may be determined. n

7 The method for detecting unbalance between two electrical networks,which consists in impressing across the said networks telegraphsignaling impulses of different frequencies, and detecting the unbalancebetween the said networks by the effect produced in a receiving circuit.f

8. The method for detecting unbalance between two electrical networks,which consists in impressing across the said networks telegraphsignaling impulses of different frequencies, and detecting the imbalancebe-y tween said networks by an indicating device in a receiving circuitcoupled to the said networks.`

9. In a duplex telegraph signaling system, the combination with a linecircuit of a plurality of terminal circuits, each comprisingI atransmitting circuit adjusted tol transmit signals of differentfrequencies, a receiving circuit, a network adapted to balance the saidline circuit, and a'relay having a. plurality of windings forelectrically connecting the said circuits, and a distortion bridgecircuit connected with a receiving circuit of one of the said terminalcircuits for determining the magnitude of the unbalance between the linecircuit and the balancing network associated with the said latterterminal circuit.

10. In a duplex telegraph signaling -K system, the combination with aline circuit of a plurality of terminal-circuits each comprising atransmit-ting circuit, a receiving cirrcuit, a network adapted tobalance the saidline circuit and means for electrically connecting thesaid circuits so arranged as to respond normally only to signals fromthe transmitting circuit of the other of said terminal circuits, andmeans connected with the receiving circuit of either terminal circuit toindicate the magnitude of the interference set up in that receivingcircuit by impulses from the transmitting circuit of the said terminalcircuit due to imbalance between the line circuit and the networkassociated with the same terminal circuit.

1l. In 'an electrical testing system, the combination with atransmitting circuit having a source of current connected therewith, aplurality of networks-connected in parallel with the said transmittingcircuit, the said networks being also connected serially with a secondsource of signaling current, a receiving circuitconnected with thesai'd'ffline circuit; :means Vfor impressing thereoii4 currentsffromboth offsaidfsources,V

and nieansrfconn'ected V.with the said receiving circuit tofldetectftlieimbalance existing between-the said-networks arising from theinterference between'f Ythe Vcurrent fromV7 the said source-'and fromthe vsaidtransmitting circuit.

12. In an electrical testing system, the

networks, arising from the interference betweenY the` current from thesaid source and from the said transmitting circuit.

13. In a duplex telegraph signaling sys- Y ,tem "comprising atransmitting circuit, av vreceiving circuit, a line circuit having asource of signaling current connected therewith, a network intended tobalance the said line circuit and a,receiving relay having a pluralityofv,windings for electrically connecting the said circuits, the method fordetermining the magnitude of the unbalance between' theline circuit andits network,

which consists in simultaneously impressing signaling impulses of adefinite frequency from said source upon said line circuit, and alsoimpressing signaling impulses of a different frequency from* saidtransmitting circuit upon said line circuit and said network inparallel, and allowing the resultant current to control the operation ofa relay, to impress upon a distortion bridge circuit-the impulses fromsaid relay and also from a source having the same frequency as the saidfirst-mentioned source, and to compare the relative strengths of thesaid impulses by4 a suitable current indicating device. f y

14. In a duplex telegraph signaling system, the combination with a linecircuit, of a distant transmitting circuit, a lioine terminal circuitcomprising a transmitter adjusted to transmit at a dierent frequencyfrom the said distant transmitting circuit, a balancing circuit, areceiving circuit, means for electrically connecting the said circuits,and a measuring device associated with the said receiving circuit tomeasure the inagniture of distortion produced upon signals received fromthe said line circuit by sigiials from the said home transmitter due tounbalance between the line circuit and the balancing circuit. Y

15. In a duplex telegraph signalingA system, the combination with a linecircuit, of

a distant transmitter, a home terminal circuit vcomprising a transmitteradiusted to transmit signals of a different frequency llU :from the saiddistant transmitter, a receiviing circuit, a balancing circuit for thesaid line circuit, a receiving relay having a plurality 'of windings forelectrically cnne-cting the said circuits, and means connected With thesaid receiving relay for measuring distortion of the received signals bythe transmitted signals, duef'to unbalance between the said line circuitand its balancing circuit. f v A Y 10 In testimony whereof, I havesigned my name to this specification this 15th day of a July, 1921. Y

HARRY NYQUIST.

